In a conventional Hard-Disk Drive (HDD) storage system, the drive receives a file to be stored, divides the file into small pieces, called sectors, encodes each sector, and writes the sector with a write head onto a storage medium. When a user wants to read the file, a read head reads the sector from the storage medium, sends it through detector and decoder blocks to obtain the sectors, forms the file, and communicates the file to the user.
The encoded sector written on the storage medium has various types of patterns, some are easy to detect and decode, and some are not. The patterns that are not easy to detect and decode define a sector failure rate (SFR) for a given application. On the other hand, the patterns that are easy to detect and decode generally do not affect the SFR while covering space on the surface of the medium.